Preheat the oven to 375 degrees . Rub the potatoes with EVOO and place on a rimmed baking sheet; bake until tender, 40 to 50 minutes. Let cool slightly. Increase the oven temperature to 400 degrees .
Halve the potatoes lengthwise. Scoop the flesh from 8 halves into a large bowl, leaving a 1/4-inch-thick shell. Scoop the flesh from the remaining 4 halves, add to the bowl; discard the skins. Mix the butter, cinnamon, ginger, cayenne and 1 tsp. salt with the potatoes. Mound 6 heaping tbsp. of the potato mixture into each potato skin.
Choose and prepare your toppings. For pepitas, toss the seeds with EVOO and salt in a bowl. For pecans, using your hands, mix the nuts with the butter and sugar in another bowl. Sprinkle the pepitas, pecans or marshmallows over the potatoes; bake 10 minutes.